This invention relates to a warning or signal light and, in particular, to a flashing signal light suitable for use in conjunction with a moving vehicle or the like.
In most visual warning devices, it is the generally accepted practice to sweep one or more beams of light through a plane of rotation. A flashing or constantly varying signal, emanating from the source, is thus presented to an observer positioned some distance therefrom. In most cases, the beam is rotated within a flat plane to alert the observer while in others the beam may be oscillated above and below the plane of rotation to produce what is called a "wig-wag" signal.
Typically, two techniques are employed to generate a moving light signal and thus create a flashing effect. The most common approach is to simply mount a number of light sources upon a rotatable platform and rotate the entire structure about a common axis of rotation. The main disadvantage associated with this type of device is the problem encountered in providing electrical energy to the individual moving lamps. This usually involves the use of complex and expensive slip ring and bushing connections which are subject to wear and dirt contamination and may also cause radio interference. Furthermore, because of the relative size and weight of the rotating structure, balancing and bearing problems are also encountered. Lastly, in order to protect the complex mechanical and electrical components from environmental contamination, it is not unusual to enclose the entire assembly in a transparent or translucent dome made of thin glass or plastic which is susceptible to breakage.
To overcome the above noted electrical problem, warning devices employing a stationary light source have been devised in which moving reflectors are passed through a stationary light beam to create a flashing effect. Although the need for slip ring connectors is eliminated, the moving structure again tends to be relatively large and complex giving rise to problems generally associated with moving a relatively heavy structure. Because of the complexity of the structure needed to rotate the reflectors it is difficult to position the light source in a location where the source can continually see the reflector surfaces. The light source usually must be positioned some distance from the reflectors and, as a consequence, some of the illumination directed at the moving targets is scattered or lost to unwanted reflections.